Seasonal prevalence of Aedes aegypti immatures in Kolkata, India

Dengue and dengue hemorrhagic fever (DHF) is recurring in India in recent years, affecting many cities including Kolkata (Calcutta). In view of this, a survey of three years was carried out on the prevalence of immatures of the vector mosquito Aedes aegypti in the city of Kolkata. Mosquito immatures were found throughout the year with fluctuating densities in the habitats surveyed. An index of density of immatures (I/S)m employed in the study revealed that in the months of August and September a peak in abundance occurs, irrespective of the habitats, with the values ranging between 1.12 and 11.4. The (I/S)m values were low during the months of April and May ranging between 0.4 and 3.8. As larval habitats, earthen containers and the sewage drains were positive throughout the year, while during the months of December to February, air-coolers and conditioners as habitats remained totally dry, without immature Ae. aegypti. The number of positive sites and monthly density between the habitat types were significantly different with an I/S- value (for a year) ranging between 2.64 (air-coolers) and 4.97 (earthen containers). The survey, while providing preliminary baseline data on immature abundance in Kolkata, calls for continuous entomological surveillance using standard protocols as carried out in Thailand for the vector management program against dengue.     

Maintenance of homeostasis for thyroid hormone in the adult rat brain: possible involvement of a nuclear-mediated phenomenon

During adult-onset peripheral hypothyroidism, the brain maintains normal levels of thyroid hormone for some time through a mechanism of 'central homeostasis'. Although onset, duration, and termination of such a homeostatic phenomenon have been recently evaluated in rat models, the mechanism behind remains unknown. During our investigation to understand the mechanism further, we injected the protein synthesis blockers actinomycin D and cycloheximide along with propylthiouracil to adult male rats during the days of onset (day 2) and termination (day 20) of the homeostatic mechanism. We evaluated synaptosomal T(3) level and neuronal Na(+)-K(+)-ATPase and acetylcholinesterase activities along with deiodinase II activity and cyclic adenosine monophosphate level in the cerebral cortex. The results indicated prevalence of unchanged or lower levels of synaptosomal T(3) on the 2nd and on the 20th day, respectively. Such a condition has been parallely supported by reflections in cerebrocortical deiodinase II activity and cyclic adenosine monophosphate levels. The activities of cerebrocortical synaptosomal Na(+)-K(+)-ATPase and acetylcholinesterase, which are the two important physiological parameters for neuronal function, have been found to be supportive of the involvement of a neuronal protein-mediated factor in the 'on' and 'off' reactions in central homeostasis during peripheral hypothyroidism. The results of our study indicate that the expression of 'central thyroid hormone homeostasis' is a genomic nuclear-mediated mechanism.